This invention is directed to a lighting fixture, particularly suitable for use in refrigerated storage units.
Supermarkets and other like establishments have walk-in refrigerated units to store fresh food products such as produce, meat and dairy products, and also to store frozen products such as ice cream and other frozen goods. Coolers typically operate at temperatures less than about 40.degree. F., and freezers at less than about 0.degree. F.
The refrigerated units have internal lighting to enable persons stocking or removing goods to see inside the unit. The low temperatures in refrigerated units and, particularly, in freezers, place special demands on lights and limit the types of lights that can be used inside them. Fluorescent lights generally do not reach full brightness ("restrike") at freezer temperatures and, accordingly, are unsuitable for this use. Other types of lights can restrike in freezers, but require a significant amount of time to do so. High-pressure sodium and metal halide lights require about twenty minutes to restrike. Consequently, these lights are typically continuously operated in freezers, resulting in high energy consumption and light replacement costs.
Incandescent lights are conventionally used in coolers and freezers. These lights have instant restrike, but have important disadvantages for freezer use. Incandescent lights generally do not have high energy efficiency, and thus are expensive to operate, and add to the cooling load on the refrigeration unit. Incandescent lights also have a relatively short service life. For example, conventional 100 watt incandescent lamps have a rated life of 1000 hours and must be replaced about nine times per year. Light replacement and associated labor costs can be significant, especially for larger supermarket chains. In addition, it is difficult to control the arc tube image in incandescent lights to produce a controlled light pattern so as to reduce dark spots in lighted areas. To increase the light coverage produced by incandescent lights, the number of lights can be increased. This approach, however, increases energy consumption and light replacement costs, and does not necessarily eliminate dark spots.
Accordingly, there is a need for a lighting fixture that can be used in refrigerated units such as coolers and freezers that (i) has instant restrike capabilities, (ii) has reduced energy consumption as compared to conventional lighting used in refrigerated units, and (iii) provides a controlled, uniform light pattern.